Monocular congenital cataracts continue to be a blinding disease in most affected eyes with the currently used surgical techniques techniques and contact lens correction. Monkey studies and pilot studies in human infants suggest an improved visual outcome can be achieved with intraocular lenses (IOLs) compared to contact lenses and pediatric ophthalmologists have begun to experiment with IOL implantation in children and even infants. However, there may be greater complications with IOLs in younger children. Therefore, this NEI Clinical Trial Planning Project proposes to develop a randomized clinical trial that will compare the relative efficacy, safety, and benefits of IOL and contact lens correction of infants with monocular aphakia to determine if and how IOL implantation might be implemented in young infants. The major endpoint of the study will be the visual outcome of these eyes. We will also compare the incidence of ocular complications, axial growth, strabismus, and the myopic shift. The proposed pilot studies during the planning project will determine surgical protocols, testing procedures, and sample sizes. In addition, pilot studies will determine the feasibility of evaluating additional parameters such as the parental stress associated with these two treatments. The pilot studies will be performed at 8 clinical center by pediatric ophthalmologists who have extensive experience implanting IOLs in children.